In the novel By the Pricking of My Thumbs, William Boscowan was a painter and the husband of Emma. One of his paintings was given to Ada Fanshawe by a Mrs Lancaster, when the latter left Sunny Ridge retirement home. It was a painting depicting the Canal house, in Sutton Chancellor.
Mr Boscowan had passed away by the time of the events of the novel, and so does not appear in person. However, he is mentioned by Mrs Copleigh. According to her, Mr Boscowan had considered buying the Canal house, and that was when he had painted the picture of it. She said that he was about forty years old, and "was a good-looking man in his way", although he had run "into fat a bit". She also said that he was a great "one for the girls".
Mr Boscowan had been keen on Mrs Charrington's daughter for a time, and he had arranged for her to attend a school in London. However, nothing had come of the relationship.
After a series of child murders happened around Sutton Chancellor, some people thought that Mr Boscowanwas the one committing them. This was because he was an artist, and people thought that artists were queer. However, Mrs Copleigh did not think it was him.
According to Tommy's friend Robert, who worked at the New Athenian Galleries, Mr Boscowan's work was very popular twenty-five years before. His paintings had sold well, and there had been plenty of shows. Then, he had gone out of fashion, and there had hardly been any demand for his works, but recently there had been a revival of interest.
According to Robert, Mr Boscowan had died when he was about sixty-five years old. He had been quite a prolific painter during his lifetime.